Mining method

ABSTRACT

A chamber mining technique whereby a series of horizontal slopes are formed between haulage and bleeder entries. Upon completion of a crosscut, the top and sides are drilled and blasted in a retreat operation and the broken ore is hauled out. The mined-out area need not be entered and there is no need for support or scaling since failure of walls between stopes will at no time endanger men and equipment.

United States Patent 91 J anssen 1 MINING METHOD [75] Inventor: AlbertT. Janssen, Dallas, Tex.

[73] Assignee: Atlantic Richfield Company, New

York, NY.

221 Filed: March 10,1971 211 App1.No.:122,927

[52] U.S. C1. ..299/13, 299/18, 299/19 [51 Int. Cl ..E2lc 41/10 [58]Field of Search ..299/2, 11, 12,13,l8,19,

[56] References Cited I UNITED STATES PATENTS 494,187 3/1893 Boyce..299/18 1 Jan.23, 1973 3,588,175 6/1971 Whiting ..299/11 PrimaryExaminer-Ernest R. Purser Attorney--B1ucher S. Tharp and Robert E. Lee,Jr.

[5 7] ABSTRACT A chamber mining technique whereby a series of horizontalslopes are formed between haulage and bleeder entries. Upon completionof a crosscut, the top and sides are drilled and blasted in a retreatoperation and the broken ore is hauled out. The mined-out area need notbe entered and there is no need for sup- .port or scaling since failureof walls between stopes will at no time endanger men and equipment.

10 Claims, 3 Drawing Figures PATENTEDJM23 I975 3, 71 2,677

INVENTOR:

ALBERT T. JANSSEN ATTORNEY mums METHOD BACKGROUND OF THE INVENTION Thisinvention relates to mining operations and in particular to a retreatmining method which can be used in place of room-and-pillar and otherconventional mining systems.

In mining flat, thick-bedded deposits of minerals, such as oil shale, adifficulty arises in that men and equipment have to move through largeunderground openings. As a consequence, these openings have to besupported and periodically scaled to render them safe for necessarymining operations. In addition, the openings left behind by conventionalmining methods, such as room-and-pillar, do not easily lend themselvesfor disposal or stowing of waste materials such as tailings or spentshale.

Obviously, whether or not any mining method is practical in the long rundepends on the economics. The method is used which is most economical ata high degree of reliability. In regard to oil shale, there has been arecent realization that the cost of roof and pillar control may make anyroom-and-pillar venture uneconomic.

What is needed is some new oil shale mining method where roof boltingand scaling operations are eliminated or minimized. Prime considerationshould be given to mine health and safety by eliminating the need of menand equipment to move in large openings and providing for uncontaminatedair to all working areas. Also, provision should be made to providemeans for disposal of spent shale in worked out areas.

SUMMARY OF THE INVENTION The present invention is based on the principlethat flat, thick-bedded deposits of minerals can be mined by driving acrosscut between haulage and bleeder entries and recovering the ore by aretreat mining operation. The broken ore is transported from the workingplace directly into the crosscut so that the resulting stope need neverbe entered by men or equipment after the ore is loaded out. Theventilation flow is from the haulage entry through the crosscut andstope to the bleeder entry. After. completion of a stope, bulkheads canbe installed at both ends and the mined out opening filled with waste,tailings, etc.

Any number of crosscuts can be driven in parallel between the haulageand bleeder entries so that a series of stopes can be in operation sideby side to attain desired production. By incorporating an overallretreat direction of mining, a high extraction percentage of theavailable ore can be obtained because the walls between chambers can bedesigned to take more pressure than pillars in room-and-pillar methods.

The mining method invented by Applicant is a much more economical systemthan room-and-pillar mining. The essential differences are that no menor equipment are required in mined-out areas so that bolting and scalingoperations are not needed in the stopes. Other advantages are the simpleventilation system and ability to use the empty stopes for wastedisposal.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a miningdevelopment according to the invention.

FIG. 2 is an enlarged section taken on line 2-2 in FIG. 1.

FIG. 3 is an enlarged section taken on line 3-3 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will be describedin conjunction with an oil shale mining operation; however, it isequally applicable and can be used to advantage in mining coal,lead-zinc, copper, or evaporites such as salt, trona,potassium,limestone, etc.

Referring to FIG. 1, a mining development is shown with stopes indifferent stages of operation in order to illustrate the overall miningmethod From drift 10, haulage entry 15 and bleeder entry 14 are drivenhorizontally into oil shale ore deposit 16. Bleeder entry 14 is extendedto an adit or shaft (not shown) connecting to the outside. From haulageentry 15, crosscuts 18 are driven toward bleeder entry 14. Uponcompletion of a crosscut, mining commences from the far end backward bydrilling and blasting ore deposit 16 to form stopes 20. After the shaleis broken loose, it is conveyed through its crosscut to haulage entry 15and then out of the mine through drift 10. Ventilation air passes uphaulage entry 15 into crosscuts l8 and stopes 20 and out of bleederentry 14 as indicated by the arrows.

When a stope is mined out, it is closed off with bulkheads 22 on eitherone or both ends in order to increase the efficiency of the ventilationsystem. Where desired, the empty stope can be utilized as a wastematerial collector or to store spent shale. If waste material isintroduced, it may be blown in from haulage entry 15 so that the dust iscarried off by bleeder entry 14; alternately, it may be hydraulicallytransported into the chamber.

FIG. 2 shows a cross-section of crosscut 18 prior to blasting. Blastholes 24 are drilled radially from crosscut 18 in upward and lateraldirections. The ends of blast holes 24 define the boundary of stope orchamber 20. As shown in FIG. 3, the blast holes are drilled at apredetermined angle to limit the throw of the blasted rocks. Ore isremoved from rock pile 26 backward through crosscut 18 prior toextending stope 20 by blasting the next section of ore. Material that isthrown too far and any large boulders are neglected.

Referring again to FIG. 1, letters A, B, C, D, E, F, and G denote stopeor chamber developments formed in ore deposit 16 in different stages ofoperation. Stope development A is the oldest while G is just starting. Gshows the startof crosscut l8 and F shows its completion. E, D, C, and Bshow the development of stope 20 by a retreat chamber mining processwhereby broken ore is collected at the stope end of crosscut 18 andcarried to haulage entry 15. In development A, stope 20 is complete andall the recoverable ore has been removed.

The dimensions of entries and crosscuts depend on space required andheading costs. The length of the crosscuts is a matter of economicssince the stopes can be unlimited in longitudinal length. Distancebetween stopes and the pillar dimensions depend on the material beingmined, overburden pressure, etc. Although pillar port should be adequateto maintain the stopes if they are to be used as storage bins. Only theentries need be bolted since the crosscuts should be stable for theircomparatively short life span. Most important, there is no need to boltthe roof of the stope or to perform any scaling operations.

By way of example, the stope dimensions may be 60 X 60 feet and thedistance between chambers on the order of 20-40 feet. The crosscutsshould be no larger than necessary to accommodate equipment, e.g. X 15feet. The angle between the crosscuts and haulage entry may be anywherebetween 90 and 45.

Belts will follow the development work as closely as possible and, inthe case of the crosscuts, are used for later stope production. Beltscan be designed in detachable sections having a length equal to theround pull. The drilling of blast holes can be accomplished by mobiledrill-jumbos with two or more drills. Since the pattern, when optimized,will be exactly the same for each stope, a high degree of mechanization,and perhaps automation, is possible.

After the shale is broken loose, it can be loaded with a front-endloader, with a side dump bucket, into a pan feeder. Thus, the loader canoperate very efficiently since it need not wait for trucks to convey theore to the pan feeder. From here the material can pass through an impactcrusher, preferably equipped with a grizzly. The pan feeder and crushershould be mobile enough to move up to some extent as loading of a roundprogresses. The crushed ore is then conveyed through its crosscut to amain conveyor in the haulage entry and out of the mine.

The basic operational steps envisioned for the mining crew are asfollows:

1. Move pan feeder and crusher rearward.

2. Shorten the belt and transport the detached section to anothercrosscut in development.

3. Drill the round.

4. Blast.

5. Move pan feeder and crusher toward the broken ore.

6. Start loading.

Many stopes can be in operation simultaneously in a stepwise manner asindicated in FIG; 1. Subsequent mining developments can be started bydriving a second haulage entry parallel to the first haulage entry andusing the latter as a bleeder entry. This process can then be repeatedas often as desired by driving a new haulage entry each time. Instead ofdriving the development into the ore body, under some circumstances itmay be desirable to start work at the periphery of the mining propertyand mine back toward the adit.

While a preferred embodiment of the invention has been shown, it isunderstood that the invention may be practiced in other ways and thatvarious modifications and changes can be made within the spirit of theinvention by those skilled in the art.

What is claimed is:

l. A method of mining thick-bedded minerals by a retreat chamber processcomprising,

a. driving a drift to a mining zone,

b. driving haulage and bleeder entries into the mining zone,

. driving approximately parallel straight crosscuts between the haulageand bleeder entries, sectionally dnllmg and blasting radially outwardlyfrom the walls and roof along the length of each crosscut, starting atthe bleeder entry and working backward toward the haulage entry toenlarge the crosscut, leaving an unmined zone adjacent thereto, and

removing the broken ore resulting from the blastmg.

2. A method according to claim 1 where ventilation flow is directed fromthe haulage entry through the crosscuts to the bleeder entry.

3. A method according to claim 1 where the resulting stopes arebarricaded and backfilled with waste material.

4. A method according to claim 1 where a plurality of stopes areconcurrently developed with new crosscuts being started when a stope ismined out.

5. A method according to claim- 1 wherein the mineral being mined is oilshale.

6. A method of mining thick-bedded materials by a retreat chamber miningprocess comprising,

a. driving haulage and bleeder entries to define the longitudinalboundries of the chambers,

b. driving a series of parallel straight crosscuts between the haulageand bleeder entries,

c. drilling and blasting the top and sides of the crosscuts to form thechambers while retreating toward the haulage entry, and

d. removing the broken ore.

7. A method according to claim 6 where the crosscuts are drilled andblasted so that adjacent chambers are in progressive stages ofdevelopment.

8. A method according to claim 6 where a bulkhead is installed at atleast one end of each chamber as it is mined out.

9. A method according to claim 6 where oil shale is the mineral beingmined.

10. A method according to claim 9 where spent shale is deposited in theempty chambers.

1. A method of mining thick-bedded minerals by a retreat chamber processcomprising, a. driving a drift to a mining zone, b. driving haulage andbleeder entries into the mining zone, c. driving approximately parallelstraight crosscuts between the haulage and bleeder entries, d.sectionally drilling and blasting radially outwardly from the walls androof along the length of each crosscut, starting at the bleeder entryand working backward toward the haulage entry to enlarge the crosscut,leaving an unmined zone adjacent thereto, and e. removing the broken oreresulting from the blasting.
 2. A method according to claim 1 whereventilation flow is directed from the haulage entry through thecrosscuts to the bleeder entry.
 3. A method according to claim 1 wherethe resulting stopes are barricaded and backfilled with waste material.4. A method according to claim 1 where a plurality of stopes areconcurrently developed with new crosscuts being started when a stope ismined out.
 5. A method according to claim 1 wherein the mineral beingmined is oil shale.
 6. A method of mining thick-bedded materials by aretreat chamber mining process comprising, a. driving haulage andbleeder entries to define the longitudinal boundries of the chambers, b.driving a series of parallel straight crosscuts between the haulage andbleeder entries, c. drilling and blasting the top and sides of thecrosscuts to form the chambers while retreating toward the haulageentry, and d. removing the broken ore.
 7. A method according to claim 6where the crosscuts are drilled and blasted so that adjacent chambersare in progressive stages of development.
 8. A method according to claim6 where a bulkhead is installed at at least one end of each chamber asit is mined out.
 9. A method according to claim 6 where oil shale is themineral being mined.
 10. A method according to claim 9 where spent shaleis deposited in the empty chambers.